The invention relates to a device for electronically executing a mathematical operation which can be executed on at the most three digital variables, two of which comprise m bits each and represent the input signals (A and B), a third variable (K) representing a weighting factor which comprises (n+1) bits (n.gtoreq.0), the mathematical operation performed on said digital variables being of the kind K.multidot.A+(1-K.multidot.B), the result Z=K.multidot.A+(1-K.multidot.B) thereof representing the digital output signal which is formed by the bit-wise execution of the mathematical operation, a partial output signal Z.sub.ij =K.sub.i a.sub.j +(1-K.sub.i)b.sub.j being obtained per bit coefficient of A(a.sub.j) and B(b.sub.j) and K(K.sub.i).
Electronic execution of mathematical operations such as additions and multiplications is known. For the execution of a combination of two or more mathematical operations it is known to execute these operations consecutively in time and to use specific means for each operation. For example, in the case of recursive digital filters where an operation of the kind ##EQU1## is to be realized, it is customary to perform the multiplication operation first, followed by the add and/or subtract operations. This requires elements such as multipliers and adders. Such an arrangement for a recursive digital filter is described on pages 40 to 46 and page 306 of the book "Theory and application of digital signal processing", by L. R. Rabiner and B. Gold, published by Prentice Hall Inc. Englewood Cliffs, N.J., U.S.A.
Due to the successive execution of the various mathematical operations in time, the processing time required is determined by the sum of the individual processing times. Moreover, the use of separate elements for the operations is an inefficient and expensive method. It is to be noted that it is also possible, of course, to use the same unit, under the control of its program, for several operations in the case of programmed processor units, but this generally requires a longer processing time. A long processing time may be a drawback, for given applications. This is the case, for example, for digital video signal processing where frequencies in the order of 35 MHz are already used in some cases. A circuit which is operational at such a frequency, therefore, offers a solution in this field of application.